Corliss Gear. 657 If the propeller sinks below the normal, water rises in D, and, compressing the air in F, presses on diaphragm H, lifting K L and moving K z round fulcrum z. Valve M being opened to steam at the bottom end, piston P is raised, thus depressing the rod s x and opening wider the engine throttle valve. But, as s moves down, the lever K z is turned round K as a fulcrum, and valve M is once more placed in mid position. Suppose the propeller rises, the air in F becomes more rare, and spring j moves L K downward, opening M at the top, bringing QR down, and raising ST, thus, partly closing the throttle valve. (See p. 1-144.) Corliss Valve Gear.—Of all the ' trip' gears,* this is probably best known. In Fig. 650 the upper diagram shews the valve gear, the lower being a section, through the cylinder and valve chambers. There are several advantages possessed by this valve arrangement and gear, some being common to other trip gears : (i) a sharp cut-off is obtained, when the 'trip ' takes place, preventing wire-drawing; (2) an easier-working form of valve, g, is adopted; (3) steam and exhaust parts being separate, there is less loss by initial condensation; (4) clearance is very small ; (5) the variable cut-off" is automatic. The valves a& admit steam, and ee pass the exhaust, being represented in plan at g. They are hollow cylinders having a * Term given to rapid cut-off gears, worked by the trip of a valve lever.